1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and particularly to a semiconductor device of a semiconductor chip laminated type wherein a plurality of semiconductor chips are laminated.
2. Description of the Related Art
A conventional bonding device and a semiconductor device both aimed at improving bonding processing of metal wires have been described in the following patent documents 1 and 2 respectively. The patent document 1 describes the bonding device in which a lead terminal mounting or placement surface of a heat coma is slanted. Since lead terminals are satisfactorily brought into contact with the mounting surface of the heat coma even if the lead terminals have warpage upon fixing the lead terminals to the mounting surface of the heat coma by a window clamper in the bonding device, heat applied from the heat coma is satisfactorily transferred to the lead terminals.
The patent document 2 describes the semiconductor device wherein four semiconductor chips are laminated. In the present semiconductor device, the uppermost semiconductor chip is fixed to lead terminals, and other semiconductor chips are sequentially shifted such that electrodes of the semiconductor chips are exposed, and fixed to the upper semiconductor chip. Since the lowermost semiconductor chip is directly placed on a heat coma in the present semiconductor device, heat is easy to be transferred to the semiconductor chips.
Patent Document 1
Japanese Unexamined Patent Publication No. Hei 7(1995)-58143 (see fourth to fifth pages and FIG. 1)
Patent Document 2
Japanese Unexamined Patent Publication No. 2001-298150 (see twelfth to fourteenth pages and FIG. 7)
Although the lead terminals can be reliably brought into contact with the heat coma even when the lead terminals are warped, in the bonding device described in the patent document 1, the present patent document 1 does not mention a problem about a case in which a plurality of semiconductor chips are laminated with being shifted from one another.
When the plurality of semiconductor chips are laminated with being shifted from one another, space is defined between a protruding portion of each semiconductor chip and a lead frame. When electrodes are laid out at the protruding portion, heat from the lead frame is hard to be transferred to the protruding portion upon wire bonding, and an ultrasonic sound applied to metal wires and electrodes also escapes to the space, so that the ultrasonic sound is not satisfactorily transferred to the metal wires and electrodes. As a result, there is a possibility that the state of connections between the electrodes of the protruding portion and their corresponding metal wires will be deteriorated. There is also a fear that upon resin encapsulation, a resin flows into the space defined between the protruding portion and the lead frame, so that the protruding portion undergoes stress, thus producing a crack in the upper semiconductor chip.
The semiconductor device described in the patent document 2 has the fear that although it has the effect of causing the lowermost semiconductor chip to directly contact the heat coma to thereby improve the transfer of heat, stress is applied to protruding portions of the respective semiconductor chips upon resin sealing, thus producing cracks in these semiconductor chips.